Admiral 24A12 restoration

[bandersen]

Originally Posted by Reece

Very nice pictures! Amazingly sharp. I noticed that set used a 6X5 in the power supply section. Those have been known to short and take out a power transformer. Here is a whole discussion about the early vs. the later version of the tube, the later "X" plate design usually deemed more rugged. One good idea is noted: provide a separate 6.3 volt transformer for the 6X5 heater, so that if it does short, it won't take out the power transformer. Some just replace the tube with a couple of diodes.

http://antiqueradios.com/forums/view...&highlight=6x5

Thanks for the reminder. You guys warned me about that tube when I picked up my Halicrafters too.

I was flipping through the production changes and discovered that Admiral added a fuse on the power supply on later runs.
They also suggest that when servicing this set to retrofit a fuse in if it's not already there.

I think I may go the diode route since it's easily reversable

[bandersen]

I dug a couple 6X5s out of my Admiral TVs. I wonder if this stacked design is any more reliable

[bandersen]

I was surprised to discover that my 24C16 Admiral uses the same chassis!



So, I order up parts for both sets and will recap them at the same time
The 24C16 is all original so I don't think I'd have the same luck if I tried powering it up

I have both the lower chassis up on the workbench and am stripping the rust and rebuilding them. Normally, I woudln;t go to these lengths, but these are really easy to take apart and reassemble.
I did find a couple fired wax caps on the amp down there so I bet this set will sound even better after the recap.
I've already repainted the transformer and polished the tube shields over on the left.


The caps I have on hand are a little too big to fit in the old cans. I did a little searching and found a line of skinny caps at Mouser that will with room to spare
I got a nice pile of orange drops too

[Reece]

If you go the diode route, you can leave the 6X5 in its socket "for pretty" and just disconnect the socket. The power xfrmr will have a little better time of it with one fewer heater to heat.

[bandersen]

Originally Posted by Reece

If you go the diode route, you can leave the 6X5 in its socket "for pretty" and just disconnect the socket. The power xfrmr will have a little better time of it with one fewer heater to heat.

Good idea. Perhaps I should do that for the 5U4 tube as well.

If I'm reading the tube data right, it looks like there's a 25 volt drop for every 100mA drawn. That means I should use a 250 ohm resistor in series with the diodes I think

[bandersen]

I've finish restoring the lower power supply + audio amp chassis. Here it is with an unrestored chassis from another set in the background.
I removed the rust from the chassis, choke and audio xfrmrs and buffed them with a non-metallic pad and WD-40. I stripped the power transformer shell and repainted it with black enamel paint. The electrolytics were restuffed and the caps below replaced. A couple out of spec resistors were replaced too.


I'm just about done recapping and replacing out of spec resistors in the top chassis too. Only a few old replacements I left in place because they tested OK.


Here's the new power resistor in the HV cage. It's a little shorter than the original so I used a wooden spacer.


Only one issue remains.
If I tune for the best picture, the audio is very weak. If I tune for the best sound, I have a lousy picture.
I haven't touched the RF/IF states yet. Maybe it's just a weak tube or a bias resistor is off ?

Otherwise, it's playing just fine. BTW Those earlier pictures look sharper because they were still frames - this is live motion.

[jeyurkon]

That power supply looks amazing! John

[zenithfan1]

Another perfect job! That power supply looks better than new.

[bandersen]

Thank guys. If you're wondering about that one black screw head - well I think those engineers meant for it to not come out. The screw head was pinched. Probably to prevent someone like me from loosening the core up to much and having all the laminated plates come apart

Any ideas about the video and audio being out of whack? Several other sets seem to suffer from the same problem. Maybe it an alignment issue or maybe my converter box is driving it too hard? I'll try my BT agile modulator tomorrow.

[jeyurkon]

Originally Posted by bandersen

Thank guys. If you're wondering about that one black screw head - well I think those engineers meant for it to not come out. The screw head was pinched. Probably to prevent someone like me from loosening the core up to much and having all the laminated plates come apart

Any ideas about the video and audio being out of whack? Several other sets seem to suffer from the same problem. Maybe it an alignment issue or maybe my converter box is driving it to hard? I'll try my BT agile modulator tomorrow.

Hopefully it's the converter box. The RF from mine is horrible. It even acts that way with a modern TV. Using a BT modulator makes a world of difference for me.

Otherwise it could be an alignment issue. Though it seems like that's not too common. I was surprised that after having to rewind a video IF transformer in my set that I didn't have to align it. It seems to work at the quessed position of the core. I expected it to be more critical than that.

John

[Reece]

Nice job on that power supply.

[bandersen]

Originally Posted by bandersen

A guy in Nebraska tried to talk me into buying that same model set and trust that it would survive shipping. I learned my lesson after destroying a similar bakelite set and turned him down...

Gee what a surprise!
Here's that very set he tried to convince me would survive shipping just fine. It was destroyed in shipping and now he's selling the remains.
I told him not to try it

http://cgi.ebay.com/Bakelite-Admiral...mZ250567121991

[bgadow]

And after all that, I see he still has UPS listed as the shipping option. No thanks!

I'll ship a small portable, but that is all. I've hardly ever heard of something like this working out well.

[jr_tech]

Originally Posted by bgadow

I'll ship a small portable, but that is all. I've hardly ever heard of something like this working out well.

Even that does not assure safe delivery... This little (12-13lb) Sony KV-5000 arrived at my house yesterday, with a broken handle, a cracked circuit board around the power plug, and the yoke shoved way back (which makes for a small "roundie" picture and rainbow effect). With a little glue, solder and adjustment, the set is pretty much ok, with a little purity issue near the right side.

So far, I have had good luck with Sony Watchmans, and nothing larger.

jr

[Dan Starnes]

First rate work and thanks for the great pics, very interesting.